1. Field of the Invention
The invention relates to a radiation detecting apparatus, a scintillator panel, and their manufacturing method and system and, more particularly, to a radiation detecting apparatus, a scintillator panel, and their manufacturing method and system which are used for a medical diagnosing apparatus, a non-destructive inspecting apparatus, and the like. In the present specification, explanation will be made on the assumption that electromagnetic waves such as X-ray, α-ray, β-ray, γ-ray, and the like are also incorporated in the purview of the radiation.
2. Related Background Art
In recent years, digital radiation detecting apparatuses each obtained by laminating, at least, a phosphor layer which emits light by irradiating an X-ray onto the surface of photoelectric conversion elements formed on a flat surface of a large area have been put on the market.
Among those digital radiation detecting apparatuses, a sharp apparatus of a high sensitivity has been disclosed in U.S. Pat. No. 6,278,118 or WO9966351A1. As such a digital radiation detecting apparatus, there has been known a photodetector (also referred to as a “sensor panel”) comprising a photoelectric conversion element unit in which electric elements such as a plurality of photosensors and TFTs (Thin film transistors) and the like are two-dimensionally arranged. There has been known a radiation detecting apparatus (also referred to as a “direct evaporation deposition type”, a “direct type”, or the like) in which a phosphor layer serving as a wavelength converter for converting a radiation into light which can be detected by the photoelectric conversion element is directly formed on such a photodetector.
As disclosed in WO200063722A1, the radiation detecting apparatus (also referred to as a “laminating type”, an “indirect type”, or the like) in which a scintillator panel obtained by forming the phosphor layer onto a supporting substrate is laminated onto the photodetector has also been known.
As a conventional typical sensor panel, a sensor panel disclosed in U.S. Pat. No. 6,278,118 is shown in FIG. 31. In FIG. 31, reference numeral 201 denotes a sensor substrate having a photosensor and a TFT; 202 a protective layer of the sensor; 203 a phosphor layer of a columnar structural crystal for converting the radiation into light according thereto; 204 a polyparaxylilene film (phosphor protective layer) for protecting the phosphor layer against the moisture; 205 a reflection layer made of a metal film for reflecting the light from the phosphor layer; and 206 a polyparaxylilene film for further improving moisture resistance. The metal film is a thin film and is evaporation deposited by a CVD method or the like.
As another conventional technique, the sensor panel disclosed in WO9966351A1 is shown in FIG. 32. In FIG. 32, reference numeral 301 denotes a sensor substrate having a photosensor and a TFT; 302 a phosphor layer of a columnar structural crystal for converting the radiation into light according thereto; 303 a polyparaxylilene film (phosphor protective layer) for protecting the phosphor layer against the moisture; 304 an SiO2 film for improving the moisture resistance; and 305 a polyparaxylilene film for further improving the moisture resistance. The polyparaxylilene film is evaporation deposited by the CVD method in a film forming evaporation depositing room.
The following points are required for the sensor panel used for such an object as mentioned above.
First, in the case of using the phosphor layer having the columnar crystalline structure made of alkali halide such as CsI:Na, CsI:Tl, and the like formed by evaporation deposition, the moisture resistance is called into question to avoid deliquescence by the moisture in the phosphor layer. The reason why the columnar crystalline structure is used as a phosphor layer is to suppress scattering or attenuation of the converted light in the columnar crystalline structure and efficiently guide the converted light to the sensor panel.
However, since the phosphor layer having the columnar crystalline structure is a hygroscopic material, there is such a problem that if it absorbs the moisture, the crystal deliquesces and the columnar crystals are joined with each other, so that the inherent light propagation is disturbed and the resolution is remarkably deteriorated.
In FIG. 32, the moisture proof in the polyparaxylilene films 303 and 305 and the SiO2 film 304 is disclosed. However, in any of the above films, the CVD method or a sputtering method is used as its film forming method.
In the phosphor layer having the columnar crystalline structure made of alkali halide such as CsI:Na, CsI:Tl, and the like formed by the evaporation deposition, there is a case where an abnormal growth (splash) defect occurs when the phosphor layer is formed. Particularly, in the radiation detecting apparatus for radiographing a human body, a thickness of 400 μm or more is necessary as a thickness of phosphor layer. In this instance, there is a case where an abnormal growing portion becomes a projective portion whose diameter is equal to 300 μm or more and whose height is equal to 20 μm or more. Further, there is a case where a doughnut-shaped concave portion having a depth of 20 μm or more is formed around the projective abnormal growing portion. The present inventors et al. have found out that a thickness of 20 μm or more is necessary as a thickness of phosphor protective layer in order to cover the abnormal growth defect portion of the phosphor layer comprising such a projective portion and a concave portion and satisfy the moisture-proofing function.
However, since the phosphor protective layer using the organic film made of polyparaxylilene as disclosed in the foregoing related art is formed by the CVD method, a film forming speed of the phosphor protective layer is equal to about 100 to 2000 Å/min and slow. Therefore, a time of 2000 to 100 minutes is necessary as a film forming time to form the phosphor protective layer of 20 μm and there is such a problem that the mass productivity is low. Further, since there are disadvantages in terms of the number of steps and costs such as material costs or the like, such a phosphor protective layer is an obstacle to reduction of costs of a product.
If the phosphor protective layer comprising the organic film made of polyparaxylilene to be used for a radiation image pick-up device of a large area (for example, 43 cm×43 cm) such as an X-ray digital camera is formed by the CVD method, inplane film thickness distribution of the phosphor protective layer increases. When a reflection layer is formed on the surface of the phosphor protective layer opposite to the phosphor, the light emitted by the phosphor layer is reflected by the reflection layer and a length of optical path of the reflection light beam entering the photoelectric conversion element is changed due to the film thickness distribution of the phosphor protective layer. Thus, since the reflecting direction of the light differs depending on the location, such a problem that the resolution deteriorates occurs.
Further, in the CVD film made of paraxylilene or the like, adhesion to the sensor protective film of the photoelectric conversion element is small, a resin to cover the periphery of the phosphor protective layer is necessary, and the costs rise.
As another requesting item, since the sensor panel converts the small amount of light into the electric signal, a high S/N ratio is required. Generally, the X-ray generating apparatus is positioned near the sensor panel in the X-ray radiographing room, there is a risk that an electromagnetic wave generated from the X-ray generating apparatus is space-propagated, enters the sensor panel from the front and rear surfaces, and is multiplexed as electric noises into the signal.